“Parkland,” Peter Landesman’s taut but unsatisfying docudrama about the Kennedy assassination, is mercifully short. For the events depicted, no matter how familiar, still hurt. Watching the movie is like enduring dental surgery without anesthesia. You clench your fists, suck in your breath and remind yourself that the pain will end. And when it does, sooner than expected, you sigh with relief.

Because the film, which affects the style of “United 93,” offers no new insights, theories or important information, you’re left wondering why it was made. I have no doubt that Mr. Landesman, a journalist and novelist who adapted the story from Vincent Bugliosi’s 2008 book, “Four Days in November,” had a high-minded rationale. The theory seems to be that by keeping most of the major turns of events off-camera and concentrating on the responses of secondary players, including doctors, nurses and federal and state officials at the scene, a story we think we know will be refreshed.

“Parkland,” named for the Dallas hospital where President Kennedy and Lee Harvey Oswald were rushed, is a considerable technical feat in which original television footage and dramatic re-creations mesh into a fairly seamless visual narrative. Except for the eloquent television commentaries by Walter Cronkite and David Brinkley, which make the squawking of most contemporary bloviators sound trite and overblown, many of the words spoken are in-the-moment reactions of everyday people under stress.

The film is especially good at evoking the chaos, panic and sickening bloodshed around Kennedy’s shooting. Zac Efron, as the doctor who desperately tries to revive the president long after he is gone, and Marcia Gay Harden, as the head nurse, give intense portraits of stunned professionals stretched to their limits.

In one of the tensest moments, Lyndon B. Johnson (Sean McGraw), sheltered by Secret Service agents, is frantically whisked to Air Force One to return to Washington in case of a coup. Aboard that aircraft, a space is carved out to make room for Kennedy’s coffin so that it isn’t treated as ordinary cargo.

Insofar as the film has a focus, it is on Oswald’s family, particularly his levelheaded brother Robert (James Badge Dale) and his kooky mother, Marguerite, whom Jacki Weaver plays as a raving megalomaniac basking in her son’s notoriety.

“I shall never be ordinary again!” she proclaims, and insists that her son be buried in Arlington National Cemetery. Ms. Weaver’s campy histrionics steal the movie, but upset its already precarious balance.

A secondary thread follows Abraham Zapruder (Paul Giamatti), the amateur photographer who shot the famous eight-millimeter footage of the motorcade. As the news media descend on him, the editor of Life magazine wins an interview with him.

Far too often, the illusion of authenticity is shattered by ham-fisted dialogue in which every note of grandiosity rings an alarm. As Jacqueline Kennedy (Kat Steffens) lingers beside her husband’s body, she is solemnly told, “It’s time to say goodbye.” When Forrest Sorrels (Billy Bob Thornton), a Secret Service agent, muses, “This was not supposed to happen,” “Parkland” collapses under it own pretensions.

In the end, there is no escaping that as the 50th anniversary of the assassination looms, revisiting the tragedy is a ripe business opportunity. The Kennedy industry grinds on, with no end in sight.

Written and directed by Peter Landesman, based on the book “Four Days in November,” by Vincent Bugliosi; director of photography, Barry Ackroyd; edited by Leo Trombetta; music by James Newton Howard; production design by Bruce Curtis; costumes by Kari Perkins; produced by Tom Hanks, Gary Goetzman, Bill Paxton, Nigel Sinclair and Matt Jackson; released by Exclusive Media. Running time: 1 hour 33 minutes.